To classify children and adolescents with diabetes as having type 1 or type 2 diabetes, and to determine how common undiagnosed diabetes is in their siblings and parents. The currently available test to diagnose type 1 vs type 2 diabetes are not always reliable. We propose to use an intravenous arginine stimulation test to measure insulin reserve and thus, differentiate between type 1 and type 2 diabetes in children and adolescents. To determine how common undiagnosed diabetes is in relatives of children and adolescents with type 1 and type 2 diabete.